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Minor Oral Surgery > LA risks > Flashcards

LA risks Flashcards

1
Q

State some instances which may lead to unwanted effects of LA administration

A
  • injecting an inappropriate solution
  • injecting too much solution
  • injecting wrong site
  • bad luck
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2
Q

What are the most serious adverse effects of LA administration

A
  • CNS problems as a result of overdose or intra-arterial injection
  • long standing nerve problems after regional block anaesthesia
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3
Q

What is the only absolute contraindication of the use of LA?

A

allergy to the solution

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4
Q

What type of LA more commonly gives rise to an allergic reaction?

A

Ester anaesthetics

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5
Q

What ester local anaesthetics are used as topical agents ?

A
  • benzocaine
  • amethocaine
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6
Q

What agent is commonly implicated in an allergic reaction during the delivery of local anaesthetic?

A

latex
which is used in the manufacture of some cartridges

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7
Q

Give examples of latex free cartridges of LA

A
  • Septanest (articaine +adrenaline)
  • Citanest (prilocaine with octapressin)
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8
Q

What should you do if a patients presents with a history that may predispose them to an allergic reaction to LA/LA components?

A
  • referral for allergy testing
  • establish a suitable alternative drug
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9
Q

Briefly explain the mechanism of reverse carotid flow

A
  • injection under strong pressure into a branch of the external carotid artery can cause some LA solution to flow into carotid bifurcation (solution travels against the arterial flow to reach the bifurcation)
  • a portion can then be redirected to the brain via the internal carotid artery
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10
Q

If patient reports tachycardia following LA delivery, how can you manage this in the future?

A

avoid the use of adrenaline containing solution

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11
Q

State a guideline for detemining the maximum dose of local anaesthesia

A

1/10th of a cartridge per kilogram

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12
Q

What organ suffers during LA overdose? Why is this

A
  • the brain
  • this is because CNS tissue is more susceptible to the actions of LA than peripheral sensory nerves
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13
Q

What are the first signs of LA toxicity?

A

excitability as the inhibitory actions of the brain are the first to be depressed

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14
Q

What are the later signs of LA toxicity?

A
  • CNS depression; this can lead to unconsciousness
  • death due to respiratory depression
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15
Q

Why is it not possible to change to another LA after the maximum dose of one has been administered?

A

this is because the effects of LA are cumulative

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16
Q

What are the injection sites for LA that cause problems?

A
  • intra-arterial
  • intravenous
  • intraneural
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17
Q

What problematic site of injection has a higher incidence?

A

intravenous

  • more common than intra-arterial
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18
Q

What is the main consequence of intra-arterial injections?

A
  • LA solution is delivered directly into the CNS
  • interference with special senses e.g.:
  • sight- double vision as orbital muscles can be affected
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19
Q

What is the cause of permanent loss of sight following intra-arterial LA delivery?

A
  • occlusion of retinal artery
  • introduction of emboli into the opthalmic artery
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20
Q

Hearing loss following LA may occur as a result of…

A
  • CNS toxicity
  • ischaemia of the cochlea following intravascular injection
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21
Q

What is the most severe consequence of intra-arterial LA delivery? What is the cause of this?

A

hemiparesis of the body

result of reverse carotid flow of LA

22
Q

What is the danger of intravenous LA delivery ?

A
  • production of systemic effects such as CNS toxicity, heart effects e.g. tachycardia and arrhythmias
23
Q

Damage to the nerve trunk following intraneural injection can be classified as…

A
  • physical- needle trauma
  • chemical- dispersal of solution into nerve bundle
24
Q

What are the consequences of intra-neural injection ?

A
  • long term anaesthesia - lack of sensation
  • parasthesia- altered sensation e.g. pins and needles
  • dysaesthesia (pain)
25
Q

Dysaesthesia is more likely following LA than surgery. True or false

A

true

26
Q

What is the consequence of penetrating both sides of a blood vessel?

A

bleeding

27
Q

What is the consequence of LA induced bleeding on the medial pterygoid muscle?

A

trismus

28
Q

What is the best way to avoid injecting into a blood vessel?

A

use of an aspirating syringe system

29
Q

State an instance where aspiration of a syringe can fail

A

aspiration may fail if the needle is blocked by the wall of the blood vessel

aspiration will occur when the tip of the needle is in the blood vessel

30
Q

Aspiration may be impeded by vessel wall obstruction. How do you manage this?

A

slow injection to prevent retrograde flow of solution

slow injection helps to reduce damage to the nerve

31
Q

Suggest the best way to prevent nerve injury

A

avoid regional block injections

32
Q

If an “electric shock” type reaction is noted on the delivery of the IANB, what should you do ?

A

no solution should be injected at that point

needle should be moved a few mm away before injecting

33
Q

Intraneural injection always produces pain and causes nerve injury. True or false

A

False

34
Q

Around __% of IANB produces an electric shock type sensation. What is the consequence of this type of sensation ?

A

8%

around 15% of people who experience this sensation experience long-lasting altered sensation of a varied duration

35
Q

__% of patients who suffer from prolonged altered sensation did not experience an “electric shock” at the time of injection

A

57%

36
Q

In what instances does LA delivery cause nerve damage?

A

when LA is injected under pressure

37
Q

What are the advantages of injecting slowly ?

A
  • less patient discomfort during infiltrations and regional block injections
  • increased efficacy of IANBs
  • reduction of systemic adverse effects
  • minimise possibility of reverse carotid flow
38
Q

What is the recommended rate of LA delivery?

A

30 seconds per ml of solution

39
Q

The higher the concentration of LA, the ________ the nerve cell survival

A

lower

reports that nerve damage is more common after the use of 4% compared to 2% solutions

40
Q

What nerve is most commonly damaged following IANB?

A

lingual nerve

accounts for 70% of the damage

41
Q

Give some reasons why the lingual nerve is more likely to suffer damage

A
  • over-reporting of such injuries happens with new drug formulations such as articaine
  • at the region of the lingula, the lingual nerve is composed of very few fascicles and in some individuals it is unifascicular at this point
  • this is unlike the IAN which is multi-fascicular at the region of the lingula

this structural difference may account for increased susceptibility of the lingual nerve

42
Q

What LA has been shown to be more effective than 2% lidocaine for mandibular infiltrations?

A

4% articaine

43
Q

There is strong evidence to suggest that 4% articaine is more effective for IANBs compared to 2% lidocaine. True or false

A

False

hence there is no advantage to using it for the IANB

44
Q

State alternatives to regional block techniques

A
  • intraligamentary
  • intraosseous
45
Q

What complications are associated with intraligamentary/intraosseous injections ?

A

damage to periodontium

46
Q

Briefly state preventative measures for preventing risks associated with LA

A
  • good medical history
  • aspirating syringe
  • limit use of regional block injections
  • inject slowly
47
Q

What is the maximum dose of 2% lidocaine (mg/kg)?

A

4.4

48
Q

What is the maximum dose of 2% mepivacaine (mg/kg)

A

4.4

49
Q

What is the maximum dose of 3% mepivacaine (mg/kg)

A

4.4

50
Q

What is the maximum dose of 3% prilocaine (mg/kg)

A

6.0

51
Q

What is the maximum dose of 4% prilocaine (mg/kg)

A

6.0

52
Q

What is the maximum dose of 4% articaine (mg/kg)

A

7.0

Minor Oral Surgery (36 decks)

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